The present invention relates to industrial process control and monitoring systems. More specifically, the present invention relates to wireless field devices used in industrial process control and/or monitoring systems.
Industrial processes are used in many industries to process or transport various materials. Industrial processes are implemented in, for example, oil refineries, food manufacturing facilities, paper pulp manufacturing facilities, etc.
Operation of an industrial process typically requires the monitoring of process variable. Example process variables include temperature, pressure, flow rate, level, etc. A process variable transmitted is used to measure a process variable and transmit information of the measured process variable to a central location. This information can used to monitor the process and can be used to control the process. For example, a valve can be adjusted using another type of field device, a control device, based upon a measured flow rate.
Traditionally, process variable transmitters have communicated with a central location using a wired connection. An example of a wired connection is a two wire process control loop in a current loop through the loop is representative of a measured process variable. Other communication techniques include transmitting digital information on the process control loop. The same two wire process control loop can be used to provide power to the field device.
Wireless field devices are used to measure process variables and communicate with another location and do not require the wired connection described above. One wireless communication technique uses a mesh network configuration. One example communication protocol is the Wireless HART® communication protocol in accordance with the IEC 62591 Standard. One benefit of a wireless device is that it does not require wires to be extended from a central control location to the field device. A further reduction in wiring can be achieved if the field device includes an internal power supply such as a battery. However, if the field device is battery operated, the device will cease operation if its power source is depleted. Therefore, it is often desirable to take steps to reduce power consumption in the field device in order to extend the life of the power source.